Fix Your Timestep!

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Sonic

So with the interest in my game on the forum, I thought I'd revive this thread to see if anyone can help me with my last stumbling block.

As I mentioned before I'm happily using the frameskip + tweening code at frame rates higher than the 60hz my logic runs at. However, when I introduce a delay of 17ms to ensure that it runs at under 60hz (and the nearest would be 30hz) it seems to jerk nastily. This is my code:


	Const FPS:Int = 60
	Const FRAMELENGTH:Int = 1000 / FPS
	Const MAX_FRAMESKIP:Int = 5
	
	Local nextframetime:Double = MilliSecs()
	Local loops:Int
	Local tween:Float

	Repeat

		' THE BIG BIT
		
		loops = 0	
		
		Local ms:Double=MilliSecs()
		
		While (ms>nextframetime And loops < MAX_FRAMESKIP)
			all.update()
			nextframetime:+ FRAMELENGTH
			loops:+ 1
		Wend
		
		tween=Float(ms+FRAMELENGTH-nextframetime)/Float(FRAMELENGTH)

		Cls
		
		all.draw(tween)

	Until 0